U.S. patent number 4,413,914 [Application Number 06/426,149] was granted by the patent office on 1983-11-08 for recovery of heavy hydrocarbons from oil sludge.
This patent grant is currently assigned to Emultec Limited. Invention is credited to Alistair D. McBride, Ian S. Ripley.
United States Patent |
4,413,914 |
McBride , et al. |
November 8, 1983 |
Recovery of heavy hydrocarbons from oil sludge
Abstract
Oil sludge (15) formed within a storage container (10) is
removed by penetrating tubular lances (20) into the sludge body
(15) and then pumping dispersant chemicals borne by a water jet
through the lances (20) into the sludge body (15) with continuous
drawing off and recirculation of emulsified fractions under
pressure. The sludge body (15) breaks down both physically and
chemically to form a pumpable fluid which is drained and mixed with
a larger volume of liquid oil to allow dispersion of the
hydrocarbonaceous content of the emulsified fluid as a suspension
in the oil volume allowing the water to settle out of the mixture,
the settled water layer being thereafter drawn off. This oil
mixture is then processed in the process plant. The dispersant
chemicals emulsify or form coloidal suspension or solution of the
hydrocarbonaceous content of the sludge body (15) in water.
Inventors: |
McBride; Alistair D. (Wishaw,
GB6), Ripley; Ian S. (Cleveland, GB2) |
Assignee: |
Emultec Limited (Cleveland,
GB2)
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Family
ID: |
10510758 |
Appl.
No.: |
06/426,149 |
Filed: |
September 28, 1982 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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228274 |
Jan 19, 1981 |
4364776 |
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Foreign Application Priority Data
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Jan 19, 1980 [GB] |
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8001862 |
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Current U.S.
Class: |
366/137;
137/577 |
Current CPC
Class: |
B08B
9/0933 (20130101); Y10T 137/86236 (20150401) |
Current International
Class: |
B08B
9/093 (20060101); B08B 9/08 (20060101); B01F
003/12 () |
Field of
Search: |
;366/134,136,137,184
;134/10,22.18,22.19,40,168R,169R ;137/577,577.5,579 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Coe; Philip R.
Attorney, Agent or Firm: Mason, Fenwick & Lawrence
Parent Case Text
This is a division of application Ser. No. 228,274, filed Jan. 19,
1981, and now U.S. Pat. No. 4,364,776.
Claims
What is claimed is:
1. Apparatus for effecting emulsification of a hydrocarbonaceous
sludge body in a container, comprising a tank for storage of
dispersant chemical, a pump having its inlet connected to a pipe
for drawing off emulsified fluid from the surface of the sludge
body in the container, a plurality of narrow bore lances for
penetrating into the sludge body in the container and each lance
connected to the pump outlet, means providing a supply of water,
and valve means interconnecting the storage tank and the water
supply means with the pump inlet whereby dispersant chemical and/or
water can be pumped under pressure along the lances and drawn off
emulsified fluid recirculated to the sludge body under pressure
through said lances, wherein the draw-off pipe and each lance is a
fluid-tight fit in a pertaining glanded nozzle, the nozzles being
mounted on a carrier plate which is releasably securable over an
opening in said container, and the draw-off pipe includes an elbow
which is securable in the pertaining glanded nozzle in any one of a
number of orientations so that the end of said pipe within the
container can be selectively relocated as required to follow the
changing level of the emulsified fluid in the container.
2. Apparatus as claimed in claim 1, wherein each lance is formed in
sections so that the length of each lance within the container can
be selectively varied.
Description
This invention relates to the recovery of heavy hydrocarbons from
the sludge which forms when oil, either crude or partly refined, is
left standing in a container.
Crude or partly refined oil is usually stored in storage tanks and
it is well known that the higher or lighter oil fractions form
layers above the heavier fractions. In the course of time these
heavier fractions become more and more viscous and form a sludge.
Similarly sludges are formed in other containers, such as
oil-filled pipelines where the oil is left standing for a long
time. These sludges play no useful part in the oil-refining and
processing plant and in fact reduce the available storage capacity
and processing rate. Where the sludge is formed in an oil tank its
presence may affect the repeated measurements which are taken of
the stored volume of crude or partly processed oil resulting in
financial penalties being paid by the proprietor. Furthermore if
the tank is of the floating roof type the sludge may form an uneven
upper surface resulting in harmful stresses on the floating roof
structure when the latter is resting on its legs.
Hitherto known methods of sludge removal include:
(1) Removal of the readily pumpable liquid oil fractions followed
by manual excavation of the sludge mass using hand tools.
(2) Circulation of hot higher-fraction oils and solvents to
dissolve at least the lighter sludge fractions.
These known methods have not proved satisfactory. The first method
is extremely time-consuming, the operatives are required to work in
an unhealthy and dangerous environment and large volumes of waste
are excavated requiring careful and costly disposal. The second
method is also time-consuming, highly energy intensive, ineffective
as regards removal of the heaviest of the sludge fractions, and can
only be practised with safety in installations specifically
designed for such extreme thermal stressing.
We have noted that the problem of dispersing oil in water has
received increased attention in recent years due to the requirement
to disperse oil spillages in sea water, one effective method of
achieving such dispersal being by the use of dispersant chemicals
such as are described in U.K. Patent Specification No. 1459104. We
have attempted sludge removal from an oil tank by circulating such
dispersant chemicals over the sludge body but we have not found it
to be satisfactory. We believe this to be because the dispersant is
not brought into intimate contact with the heaviest of the
fractions in the sludge body.
We have however surprisingly discovered that by penetrating tubular
lances into the sludge body and then pumping such dispersant
chemicals borne by a water jet through the lances into the sludge
body and by continuously drawing off and recirculating the
emulsified oil fractions under pressure, the sludge body can be
broken down both physically and chemically so as to form a pumpable
mass which can be drained from the container in which the sludge
body was formed.
Accordingly the present invention provides a method of removing a
hydrocarbonaceous sludge body from a container, comprising the
steps of penetrating one or more tubular lances into the sludge
body, pumping into the sludge body by way of the tubular lances
dispersant chemical borne by a water jet, the dispersant chemical
being emulsifiable in water, continuously drawing off the
emulsified hydrocarbonaceous fractions from the surface of the
sludge body and recirculating these fractions under pressure by way
of the tubular lances into the sludge body.
Preferably the dispersant chemical contains alkyd resin and
conveniently is prepared in the manner described in any one of the
examples recited in U.K. Patent Specification No. 1459104.
Conveniently the drawn off emulsified hydrocarbonaceous fractions
are subjected to a mechanical process to reduce the size of the
solids content prior to being recirculated under pressure through
the tubular lances. The recirculated material may also be subjected
to a controlled amount of heating. Because the heated material is
recirculated into the sludge body the heat is dissipated therein
relatively quickly and the installation is not subjected to extreme
thermal stressing.
Conveniently prior to the dispersant chemical being pumped into the
sludge body the higher fractions of the sludge body are removed by
washing with crude or gas oil.
The present invention also provides a method of recovery of heavy
hydrocarbons from the sludge which forms when oil is left standing
in a container, comprising emulsifying the sludge body by the use
of water and dispersant chemicals which are emulsifiable in water,
mixing the emulsified fluid with a larger volume of oil so as to
allow dispersion of the hydrocarbonaceous content of the emulsified
fluid as a suspension in the oil volume, allowing the water to
settle out of the mixture, and thereafter drawing off the settled
water layer.
Preferably the volume of oil with which the emulsified fluid is
mixed is contained in a container into which the emulsified fluid
is pumped to achieve said mixing. Conveniently the oil is crude oil
or gas oil.
The present invention also provides a method of processing in a
processing plant oil housed in a container which comprises the step
of recovering the heavy hydrocarbons from the sludge which forms
when oil is left standing in the container by the use of dispersant
chemicals which are emulsifiable in water, and processing in the
process plant the recovered hydrocarbon/chemical mixture when
suspended in an oil carrier, the dispersant chemicals being
selected from the group which is compatible with the processing
plant.
Conveniently the dispersant chemical is one of the formulations
recited in U.K. Patent Specification No. 1459104.
The present invention also provides apparatus for effecting
emulsification of a hydrocarbonaceous sludge body in a container,
comprising a tank for storage of dispersant chemical, a pump having
its inlet connected to a pipe for drawing off emulsified fluid from
the surface of the sludge body in the container, a plurality of
narrow bore lances for penetrating into the sludge body in the
container and each lance connected to the pump outlet, means
providing a supply of water, and valve means interconnecting the
storage tank and the water supply means with the pump inlet whereby
dispersant chemical and/or water can be pumped under pressure along
the lances and drawn off emulsified fluid recirculated to the
sludge body under pressure through said lances.
The present invention also provides an oil storage tank the wall of
which comprises an opening with an externally removable plate
thereover, the tank being modified by removal of the removable
plate and replacement thereof by a plate containing a plurality of
glanded nozzles the nozzles being sized to retain in a fluid-tight
manner the draw-off pipe and the narrow bore lances of the
preceding paragraph.
An embodiment of the present invention will now be described by way
of example with reference to the accompanying drawings, in
which
FIG. 1 is a plan view of a storage tank with sludge recovery
apparatus connected thereto;
FIG. 2 is an elevational cross-section of the tank of FIG. 1;
FIG. 3 illustrates a glanded plate used in FIG. 1;
FIG. 4 is a sectional view of the plate of FIG. 3 showing the
glanded nozzles in greater detail; and
FIG. 5 is a sectional view of an alternative form of nozzle
arrangement.
In FIGS. 1 and 2 of the drawings an oil storage tank 10 is formed
by a peripheral wall 11 and a floating roof 12 which has legs 13.
Within the tank 10 adherent to the floor 14 thereof is a sludge
body 15 which is to be removed. For this purpose the maximum volume
of pumpable oil within the tank is removed by pumping so that the
roof 12 assumes the position shown in FIG. 2. By means of access
through the roof 12, conveniently at the legs 13, the profile of
the sludge surface 16 is determined and samples of the sludge are
withdrawn for chemical analysis. With the profile of the sludge
surface 16 determined, several access points 17 in the wall 11 of
the tank 10 are selected at which there are existing openings with
externally removable cover plates. These openings may be manholes
or, as in FIG. 2, a mounting for a conventional equipment such as
an agitator or mixer. The existing cover plates are removed by
releasing the bolts securing these plates in position and are
replaced by special plates 18 (FIG. 3) containing a plurality of
glanded nozzles 19. Removal of the existing plates is possible
either because they lie above the surface 16 of the sludge body 15
or if they lie below the surface 16 a temporary cover plate is
slipped between the skirt of the floating roof 12 and the inner
surface of the wall 11 so that there is minimal spillage from the
tank 10 during this procedure. The plates 18 are positioned around
the wall 11 of tank 10 in spaced locations and permit entry of
tubular lances 20 of relatively narrow bore into the tank 10 within
the body 15 of sludge as indicated diagrammatically in FIG. 2 so
that the ends of the lances 20 lie in the vicinity of the peak of
the surface 16. Conveniently the lances 20 are made of a
noncorrosive plastics material such as ABS formed in sections so
that the length of each lance can be increased or decreased as
desired. For example each lance section may be internally
screw-threaded at one end and externally screw-threaded at the
other end, the outer diameter of the lance throughout its length
being substantially constant so that the lance is a fluid-tight fit
in the pertaining glanded nozzle 19.
A relatively large-diameter suction pipe 21 is entered through the
pertaining glanded nozzle 19 in each plate 18 and is directed
through the sludge body 15 to draw off pumpable fluids gathering on
the surface 16. At each plate 18 the lances 20 and the suction pipe
21 are connected to a pump 22, via valved pipework 23, as is a tank
24 containing dispersal chemical and a water supply pipe 25.
The glanded nozzle 19 which accommodates the suction pipe 21 is
formed by a stand-off pipe 26 (FIG. 4) welded at one end to the
plate 18 and at the other end to a flange 27. The suction pipe 21
is of fixed length terminating at the plate 18 in a metal section
which includes a bend or elbow which incorporates a flange 28 which
can be bolted to flange 27 in any one of a number of orientations
in order that the orientation of pipe 21 within the tank can be
varied in steps to locate the end of suction pipe 21 in a desired
position. The space formed between pipe 21 and the stand-off pipe
26 includes packing (not shown) so that the pipe 21 is retained in
the nozzle 19 in a fluid-tight manner. In order to provide for
continuous positional adjustment of the end of suction pipe 21
within the oil tank the flange 28 may be mounted on the pipe 21 by
means of screw threads 29 (FIG. 5) and a locking ring 30. Thus the
flange 28 may be permanently secured to nozzle flange 27 and
adjustment of the pipe 21 provided by releasing the engagement of
the locking ring 30 with the flange 28 and thereafter rotating the
pipe 21 to the required position.
The composition of the dispersal chemical is determined from the
previously taken sample of the sludge and is suited to the
composition and physical characteristics of the sludge and the
down-stream oil-processing plant in which the emulsified sludge
will ultimately be used.
By way of example the dispersal chemical may be formulated as
follows:
An alkyd resin (A) is prepared from pentaerythritol, glycerol,
polyethylene glycol (molecular weight Mn 600), trimellitic
anhydride and coconut fatty acids in a molar ratio of
0.6:0.6:1.2:1.2:3.0 respectively so as to give a polyethylene
glycol content of 40% by wt. The resin had an acid value of 18 to
22 mg KOH/g, and a (POH PA)e value of 1.0.
A second alkyd resin (B) was prepared in the same manner replacing
the coconut oil fatty acids by soyabean fatty acids and in this
instance the polyethylene glycol content was 50% by wt.
Using resins A and B, the following formulation was blended:
(1) Resin A 6 parts by wt (as a 75% solids solution in white
spirit)
(2) Resin B 4 parts by wt (as a 95% solids solution in white
spirit)
(3) *Teefroth AN (reaction product of propylene oxide and methanol,
containing an average of 3.7 molecules of propylene oxide per
molecule of methanol) 20 parts by wt.
(4) NP6 (6 mole ethylene oxide alkoxide derivative of nonyl
phenol)--10 parts by wt.
(5) Heavy aromatic hydrocarbons--60 parts by wt.
To effect removal of the sludge body 15 from the tank 10 the
dispersal chemical is pumped into the body 15 through lances 20
borne on a water jet resulting in partial emulsification of the
body 15. The emulsified liquids gather on the surface 16 where they
are collected by suction pipe 21 and recirculated along the lances
20 under the pressure imposed by the pump 22. This process is
repeated continuously utilising a predetermined volume of dispersal
chemical for the estimated volume of the sludge body 15 and
thereafter water is added to the recirculating fluids, the
recirculation being continuous until such time as the entire body
15 is emulsified and is in the form of a pumpable fluid, as
determined by intermittent tests made by dipping through one of the
access points in the roof 12.
By way of example it is estimated that for 2,000 tons (tonnes) of
sludge about 50 tons (tonnes) of dispersal chemical and 7,000 tons
(tonnes) of water is required using a pump with an output pressure
of about 50 psi g. (3.5 bar). Conveniently the suction pipe 21 is
about 6 inches (15 cm) diameter and there are four lances 20 each
about 4 inches (10 cm) in diameter, the lance outlets being of
reduced diameter, for example 2 inches (5 cm) in diameter. The wall
thickness of the suction pipe and of the lances conveniently is
about 0.5 inches (1 cm) and each lance outlet incorporates a
non-return valve mechanism to prevent ingestion of sludge as the
lance is entered into the sludge body 15. The suction inlet to the
pump 22 may incorporate a device for reducing the size of solids
transmitted through the pump and a heater may be connected to the
pipework 23 to raise the temperature of the recirculated fluids to
about 30.degree. C.
When the sludge body 15 is completely emulsified the emulsified
fluid is pumped by way of an existing outlet in the tank 10 to be
mixed with a larger volume of oil stored in another storage tank
(not shown) as a result of which the hydrocarbonaceous content of
the emulsion is dispersed in the sotred oil and retained in
suspension therein whilst the water content of the emulsion settles
out and can be drawn off and disposed of as clean effluent. The
stored oil containing the emulsified sludge and chemical in
suspension is then available for use as raw material in the
down-stream oil processing plant. During the pumping out of the
cleaned tank it is desirable to maintain the pumps 22 in operation
in order to prevent the sludge settling out of the emulsified
fluid.
It will be understood that various modifications may be made to the
embodiment within the broader concepts of the invention. For
example the invention may be practised where the stored oil is
contained in a lagoon or underground cavern the boundary being
defined by natural rather than man-made formations. In this case it
is clearly not practical to enter the lances through the side wall
of the container but the invention may be practised by directing
the lances into the sludge body from any direction--conveniently
from above. Furthermore the sludge need not be formed from crude
mineral oil since other oils, such as heavy fuel oil and fish oil,
give rise to sludges which can be treated similarly. The dispersant
chemical may be any one or a mixture of polymeric surfactants in an
oxygenated alyphatic solvent.
Where the invention is practised on a sludge body within a closed
oil storage tank the entire recovery process can be carried out
without the need for operating personnel to enter the tank; a
gas-free atmosphere within the tank can be provided on completion
of the process; spillages of hydrocarbonaceous material in the
vicinity of the tank is minimal; and the effluent water after
completion of the process is sufficiently clean for disposal
through the normal refinery effluent treatment system. The water
used in the recovery process may be either fresh or salt water and
because the process is water-based the fire risk arising from the
invention is minimal. Economically, the invention permits recovery
of the sludge body in a form which is usable in the oil-processing
plant and the down-time of the tank being cleaned is only one third
or one quarter that required of the prior art manual method.
We have used the term `emulsifiable` herein in relation to the
dispersability in water of the dispersant chemical to indicate that
the dispersant chemical is substantially uniformly dispersable in
the water in the form of a colloidal suspension or a solution.
* * * * *